Croup in Babies and Young Children: Symptoms, Treatment, and When to Go to Hospital

Croup is one of those conditions that is immediately recognisable once you have heard it — and genuinely alarming if you have not. The distinctive seal-like barking cough, often appearing in the middle of the night, is one of the most distinctive sounds in paediatric medicine. This guide explains what croup is, what causes it, what actually helps, and when it becomes an emergency.

What Is Croup?

Croup is a viral infection of the upper respiratory tract — specifically the larynx (voice box) and trachea (windpipe) — that causes inflammation and narrowing of the airway just below the vocal cords. The narrowed airway is responsible for two characteristic symptoms:

The barking cough. Often described as sounding like a seal or a dog barking, this distinctive sound is caused by air moving through the inflamed, narrowed larynx. It is unlike a normal cough and parents who have heard it once rarely need to have it explained to them.

Stridor. A high-pitched, noisy breathing sound heard on inhaling, caused by air being drawn through the narrowed airway. Stridor is distinct from the barking cough — it occurs between coughs, during normal breathing. It is most noticeable when the child is breathing in.

Many children also have a hoarse voice, a fever, and typical cold symptoms (runny nose, mild temperature) in the day or two before the croup symptoms appear at night.

Who Gets Croup and When?

Croup is most common in children aged six months to three years, with the peak incidence around eighteen months. It can occur in older children but is less common. It is unusual but possible in young babies under six months.

Croup is more common in autumn and winter, peaking between October and March in the UK. It tends to arrive at night, often waking children from sleep — this is because lying flat and the relaxation of sleep allow secretions to pool near the airway, and the larynx tends to narrow further in the horizontal position.

The commonest cause is parainfluenza virus, though croup can also be caused by RSV, influenza, adenovirus, and other respiratory viruses. It is contagious — spread by respiratory droplets.

The Steam Bathroom: A Persistent Myth

For many years, sitting with a child in a steamy bathroom (running the hot shower with the door closed) was standard advice for croup. Many parents still reach for this approach, and it is widely shared in parenting communities.

However, the evidence does not support steam as a treatment for croup. A well-conducted randomised controlled trial published in the journal Emergency Medicine found no benefit from steam inhalation over standard care. The current NHS guidance and guidelines from paediatric emergency medicine do not recommend steam treatment.

Beyond the lack of efficacy, there is a genuine safety risk: children treated with steam in bathrooms have been burned. The steam bathroom approach should be abandoned.

What Actually Helps

Cool night air. Mild croup often improves when children are taken outside into cool air, or when a window is opened to bring cool air into the room. This is one reason why parents sometimes find that their child's symptoms seem better by the time they reach the hospital — the car journey in the cool night air has already helped. The evidence base for cool air is not conclusive, but it is widely observed clinically and poses no risk.

Keeping the child calm. Crying, agitation, and distress significantly worsen stridor by increasing the work of breathing and causing the inflamed airway to narrow further. Staying calm yourself, holding and comforting your child, and keeping the atmosphere quiet and reassuring can meaningfully reduce the severity of symptoms.

Dexamethasone (steroid). The main medical treatment for croup is an oral corticosteroid — typically a single dose of dexamethasone. Steroids reduce airway inflammation significantly and are highly effective. Even children with mild croup who come to an emergency department are now routinely given a single dose of dexamethasone, because evidence shows it reduces symptom duration and the likelihood of return visits. If your child's GP or emergency department prescribes a steroid, this is best practice.

Adrenaline (epinephrine) nebulisation is used for severe croup and provides rapid but short-lived relief while other measures take effect.

When to Seek Help

Go to A&E or call 999 if your child:

• Has stridor at rest — that is, the high-pitched noisy breathing is continuous, even when calm
• Is working hard to breathe — you can see the neck muscles straining, or the skin between the ribs pulling inward with each breath (called intercostal recession)
• Has blue or grey colouring around the lips or fingernails — a sign of low oxygen
• Is drooling excessively and cannot swallow (this is more associated with epiglottitis, a different and more serious condition, than classic croup)
• Is unusually limp, unresponsive, or very difficult to rouse

See a GP or call 111 if:

• Symptoms are moderate and you are worried
• Croup has lasted more than three to four days without improving
• Your child has recurrent episodes of croup
• Your baby is under six months old and has croup symptoms

Manage at home with calm, reassurance, and cool air if the croup is mild — the barking cough is present but there is no stridor at rest, no significant difficulty breathing, and your child is alert and not distressed between coughing episodes.

Prognosis and Recurrence

Most episodes of croup resolve within three to five days with simple measures. Medical treatment shortens the course significantly. Croup does not typically leave any lasting airway damage.

Some children have recurrent croup — sometimes called "spasmodic croup" — which may be triggered by allergens as well as viruses. If your child has had croup more than once, discuss this with your GP, as there are some cases where further investigation is warranted.